I bought one of those "Barker Breakers" that a few mentioned on this site. My Yorkie is quiet, it's my Maltese that's the barker and we've tried EVERYTHING, except a shock colar which I refuse to ever do. The Barker Breaker emitted a very high pitched noise when he would bark. It worked like a charm for about 5 days and then he just learned to bark louder than Barker Breaker noise! So we're back to square one.